1. Field of the Invention
This invention relates to thrust bearings, and more particularly concerns thrust bearings having a leading edge oil distribution groove.
2. Description of the Prior Art
Prior to Kingsbury's LEG thrust bearings, conventional thrust bearings were lubricated by feeding oil into passageways in the base ring that lead to the shoes, and flooding the inside of the base ring and the shoes with oil. However, this system of lubrication consumed a large quantity of oil and created a large power loss.
Kingsbury's LEG thrust bearings, which are described in Kingsbury's U.S. Pat. No. 4,501,505, which is incorporated herein by reference, overcame the drawbacks of these conventional thrust bearings by providing oil lubricant where it is needed and used, at the working face of the shoe, rather than by flooding the inside of the base ring and the shoes with oil, resulting in a reduction in the amount of lubricating oil needed and a reduction in the frictional power losses, permitting operation at lower film temperatures, and increasing the load carrying capacity of the bearing.
In practice, Kingsbury's LEG thrust bearings have worked well over the years in many high-speed turbo-machinery applications. However, industry trends have been to design higher speed machines that are commonly tested under low load conditions prior to field application. At certain high speed/low load conditions (e.g. speeds above 275 feet per second at the mean diameter of the thrust bearing and thrust loads less than 100 psi unit loading), we have noticed that higher oil supply pressures are required for the LEG at the design oil flow and that when higher thrust loads are eventually applied, the oil supply pressure drops to normal levels. If the machine's lubrication system can not accomodate the higher oil supply pressures, the bearing receives less than design oil flow at high speed/low load conditions which causes higher film temperatures.